Apparatus for drying webs of pulp on sieves of drying machines



Apnl 8, 1958 A. STAUDENMAIER 2,829,567

APPARATUS FOR -DRYING wEBs oF PULP ON SIEVES DRYING MACHINES Filed rch 17, 195s Bg @L Atornegs United NStates Patent O APPARATUS FOR DRYING WEBS F PULP 0N SIEVES OF DRYING MACHINES Alois Staudenmaier, Ravensburg, Germany, assignor to Escher Wyss G. m. b. H., Ravensburg, Germany, a corporation of Germany Application March 17, 1955, Serial No. 495,023

Claims priority, application Germany March 24, 1954 5 Claims. (CI. 92-52) The invention relates to an apparatus for drying webs of pulp on sieves of drying machines, more especially of paper, board and pulp drying machines and for drying water-permeable fabrics and the like.

`The drying of webs of pulp on machine wire sections is conventionally elected by means of so-called tube rolls with plane suction devices connected thereto, which sometimes act as free-fall suction devices, but are generally connected to vacuum pumps. The degree of drying may be Varied within certain limits by varying the height of the vacuum.

Therefore, the atmospheric air pressure acts from above as super-pressure on the pulp web and thus on the sieve cloth and must be taken up by the covering of the suction device. The friction thus produced between the moving sieve cloth and the xed coating of the suction device has an equally unfavourable effect both on the sieve cloth and on the coating of the suction device. The force required to overcome the friction is very considerable.

These facts, which are well known to any person skilled inthe art, have led to numerous attempts to` provide arrangements for overcoming this disadvantage, but the problem has not hitherto been satisfactorily solved in all respects. Many types of cylindrical suction devices are known which afford advantagesin regard to the friction, but the distance between the rollers carrying the sieve cloth has proved toogreat and maintenance of a seal has always afforded difficulties.

Even devices for passing protective interlayers in the form of an endless water-permeable band or supporting apron between the sieve and the suction device at the speed of the sieve, while being capable of eliminating the friction detrimental to the sieve, cannot eliminate the actual frictional work. Although the frictional work between the endless supporting apron and the covering of the suction device is less than that between the sieve and the covering of the suction device, it is set up over the entire width of the web and is therefore still very considerable. i

Suction devices are also known, in which the actual suction member is an elastic endless apron which has grooves open towards the suction face, i. e., the face engaged by the sieve cloth and extending across the width of the web. It is carried along by the sieve cloth at the speed of the latter by adhesive action, the pulp water being sucked off by vacuum action at the ends of the grooves, that is to say at the side edges of the apron. The elastic endless apron travels over rollers and is also supported by supporting rollers at the centre. The frictional work to be overcome in such cases is extremely small, since it is only caused by the bearing friction of the rollers and supporting rollers mounted in roller-type bearings. With this type of suction device, there is no friction at all between the machine wire and the suction member. Apart from the bearing friction already mentioned, friction is only set up to a small extent at the suction heads at the side edges of the' endless apron.

2,829,567 Patented Apr. 8, 1958 rice The overall height of the said apron, however, must not be too great, since its elasticity would otherwise sulfer.

The only diiiiculty hitherto arising in the operation of l such suction devices resides in that a constantly good seal between the side edges of the endless apron and s the fixed suction heads has not been obtained, because the overall height and consequently the sealing surfaces are too small.

The present invention has for its object to obviate this hitherto existing diticulty, so that a constantly good seal and consequently optimum operating conditions in all respects may be simultaneously attained with minimum expenditure of force and with the least possible adverse effect upon the sieve cloth.

In an apparatus for drying webs of pulp on endless sieves of paper, board and pulp drying machines and for drying water-permeable fabrics and the like, with an elastic endless apron which is transversely ribbed on its suction side, so as to present to the sieve cloth grooves extending across the Width of the web, and suction heads laterally adjacent thereto, this object is achieved in accordance with the invention by virtue of the fact that there is a shroud strip connected with the tops of the ribs, overlying the ends of the grooves and projecting beyond the lateral edges of the apron to overlie and seat upon xed sealing surfaces on the suction heads. Thus, the apron affords two seals, one between the projecting shroud strips and the suction heads, and the other between the underside of the endless apron and the suction heads. Between these two seals the ends of the grooves are in free communication with the suction heads.

A constructional example of an apparatus designed in accordance with the invention is illustrated in simplilied form by way of example in the accompanying drawings, in which: i s

` Figure l shows a cellular band suctiondevice in side elevation.

Figure 2 is a section on a larger scale through the snction head on the line lI--lI of Figure l.

Fig. 3 is` a perspective View of a fragment of the edge of the apron, looking from beneath.

Figure 4 is a cross-section through the lateral packing point on a larger scale than Fig. 2, and on the line IV- lV of Figure l.

The illustrated drying apparatus comprises an elastic endless apron 1, which is passed over two rollers 2 and is supported between these rollers on two supporting rollers 3. The apron 1 has tranverse ribs on its upper face, between which ribs are openetopped grooves 4 extending across the width of the web. Later-ally adjacent plates 5 are designed as suction heads 6, by which the water accumulating in the grooves 4 is sucked olf in the drying of a pulp web 8 passed over an endless sieve cloth 7. The connecting pieces 9 establish the connection to a suction pump not shown.

ln the case of narrow paper machines, unilateral suction is suflicient. ln the case of wide machines, however, the suction will always take place on both sides. In the illustrated constructional form of the drying apparatus, as illustrated in Figure 2, a tube 10 is provided to connect the suction head 6 to the similar and opposite suction head (not shown). The connecting pieces 9 therefore only have to be provided on the driving side.

Spindles 1l serve. to actuate the throttling members (not shown) fitted in the connecting pieces 9 from the operators side. The suction surface is subdivided in the longitudinal direction into individual sections 12, 13, 14, 15, 16 and 17, in which any desired vacuum can be produced by appropriate adjustment of the throttling members fitted in the connecting pieces 9.

A strip 18, thinner than the depth of the grooves 4 is connected with the tops of the transverse ribs between which the grooves lie, and preferably the strip' has its top surface flush with the tops of the ribs. This strip overlies the end portions of the grooves 4, and has a portion 19v which projects horizontally beyond the corresponding edge of the apron 1, so as to overlie a sealing member 2t) formed on the suction-head housing 5. By this arrangement, it is possible to dispose the surfaces for the seal horizontally instead of vertically as hitherto and to make them sufciently wide even if the elastic apron is of small over-all thickness. The seal between the endless grooved apron 1 and the lateral suction heads 6 takes place on the underside of the projecting part 19 of the shroud-strip 18, which part bears on the sealing surface 2t), and on the underside of the elastic apron near its lateral margin, where it bears against a sealing surface 21.

The sealing surfaces 20 and 21 also have channels 22, 23 which permit an additional water lubrication, the water being fed through a channel 24. The said water not only serves the purpose of effecting a lubrication of the sliding surfaces, but also has an air-excluding effect itself, since only Water can penetrate into the suction head 6 through any narrow clearances.

The shroud strip 18, 19 moves with the apron 1, and is connected therewith as indicated in the drawing. Integral construction, though considered desirable, is not essential.

While a surface conguration for apron 1 aifording straight transverse grooves is preferred, no novelty is claimed for that detail. It is important that the channels afford flow paths which lead to an edge or to both edges of the apron. The seal, however, is not with the edge surface as heretofore. Instead, there are two seals, spaced apart, so as to lie in different horizontal planes, a feature which permits the use of adequate sealing areas, even with a very thin apron.

What is claimed is:

l. Supporting means for the traveling dewatering screens of paper-making and similar machines, comprising in combination with the sieve cloth of said machine, a traveling exible apron having a channeled upper surface ou which the sieve cloth rests and with which it travels, said channelling affording flow paths leading to at least one lateral edge surface of the apron, said paths adjacent said edge being overlaid but not blinded by a exibie substantially impervious'shroud stripwhich is connected with the apron at points between said channels, supports a portion of the screen cloth adjacent an edge thereof and projects laterally beyond the lateral edge surface of the apron; and a suction box having means to support and guide said apron, saidmeans affording a guide surface underlying and engaging the shrouded edge portion `of the apron and a secondary guide surface laterally and vertically offset from the first-named guide surface and underlying and engaging the projecting portion of the shroud strip, there being suction passages which pass through the space .afforded by said offsets and lead to the edge surface of the apron and there communicate with the ends of said flow paths.

2. The combination defined in claim 3 in which both lateral edges of the apron carry shroud strips and the supporting means of the suction box include parallel guide surfaces beneath each edge of the apron and beneath each shroud strip, whereby the water otf-ow is divided, and the necessary over-all thickness of the apron is mini miZed.

3. The combination defined in claim 1 in which cach of said guide surfaces has a longitudinal channel and means are provided to feed Water to said channels.

4. The combination defined in claim 1 in which the surface channels on the apron are grooves between upstanding ribs and the shroud strip is connected with the top portions of said ribs.

5. The combination defined in claim 1 in which the surface channels on the apron are grooves between upstanding ribs and the shroud strip is connected with the top portions of said ribs with its top surface ush with the tops of the ribs.

References Cited in the le of this patent UNITED STATES PATENTS Un 5 DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 2,829,567 April 8 1958 Alois Staudenmaer It is hereby certified that error appears in the printed specification of' the above numbered patent requiring correction and that the said Let sers Patent should read as corrected below.

Column 4, line 16, for the claim reference numeral "[3" reed lem Signed and sealed this 20th day ofb Mey l958 (SEAL) Attest:

KARL Ha AXLINE ROBEFJT C. WATSON Attesting Officer Conmiseioner of Patents 

